The career of a hero begins with a Call to Adventure, a catalyst that pushes him from his ordinary life toward extraordinary things. Several posts back, in a ramble about character background skills, I alluded to the common fantasy RPG custom of adventurers starting young. In most games I've played, both as DM and player, the expectation is that human characters receive their Call to Adventure in their mid teens to early twenties. There are several good reasons for this convention, both in role-playing and practical meta-gaming terms. Youth is often the time of restlessness and of rebellion against norms and expectations. Young people are typically just peaking in terms of physical development. Their lack of any appreciable trade skills makes any but the most cursory of skill systems unnecessary. By the time they reach their 30s and 40s, if not before, those who survive the rigors of an adventuring career are generally expected to settle down, either to take up an honest trade, to live a life of ease on the proceeds of their exploits, or for the most successful and fortunate, to rule.
Yet fiction is not lacking for heroes who buck this pattern mightily. Sometimes the Call to Adventure passes by and leaves them untouched through their youth, and they remain oblivious to it or even count themselves fortunate that it has spared them. While their restless peers go out to seek fame and fortune or grisly death in dungeon and wilderness, they live respectable, ordinary lives. They learn their trades, perhaps get married and have children, abide the law of crown and church, and pay their taxes. Only when the courses of their lives seem comfortably set does the Call to Adventure come again, and this time despite their best efforts, it finds them.
Many, if not most of us in the OSR can identify intimately with a more mature character, being of an age with them. (I'm but a month and a half shy of my 39th birthday, myself.) There's really no reason in the world why a PC shouldn't be able to begin as a first-level character in his or her 30s or older, and probably more than a few of you reading this have done so. Nonetheless, I think it's worth pondering the differences between running such a character and a more conventional brash young adventurer.
What might prompt a person to turn his back on the safe and familiar life he's built for himself over the course of a few decades? Perhaps it's boredom with a routine that's become too familiar, or a long-latent regret for paths not explored in youth - something akin to what we might call a midlife crisis. A character might be faced with bankruptcy or loss of livelihood, and turn to adventure in desperation. A loss or personal tragedy might lead to a desire for vengeance or a sense of "nothing left to lose." This loss could be as great and epic as one's home town being destroyed by monsters or an enemy army, or as mundane as being deserted by a spouse or partner. A public disgrace for some misdeed, whether or not the character is actually guilty, could lead her to exile herself from polite society and seek redemption in heroism. Or perhaps, like Bilbo Baggins, the character might be sought out for some skill he has that an adventuring party needs, and discover, however reluctantly, that adventure suits him better than he ever imagined it would.
Unlike the young adventurer, the character of advancing years might well have attained journeyman or master status in some craft or profession. A character with a skill corresponding to one of the categories of hirelings in the rules should be able to function as an expert in that field; i.e. a character coming from a career in sailing could act as the skipper of a vessel, while a blacksmith could craft weapons and a horse trainer can break mounts to the saddle. The player might just as easily choose a less useful skill for his or her character, though, or might decide that the PC never found a true calling in years of dabbling.
A character well-established in the community, with a long-practiced vocation, may start with different resources than a fresh-faced youngling. The blacksmith might make himself a sword or shield for half price; the horse trainer might have access to a pack horse; a merchant might have an extra 1d6x5 starting gold. The character will probably have a few contacts in the local area, neighbors, clients, colleagues, and the like. Even a disgraced character is likely to have one or two loyal friends who stand by him or her, even if not publicly. The number and loyalty of such contacts should be affected by the PC's Charisma - perhaps 1d4 contacts plus an additional 1d4 per point of Ch bonus, with loyalty judged according to the retainer morale score for the character's Charisma score.
Of course, starting late in life has its disadvantages too. Most obviously, physical abilities begin to deteriorate. Some editions have a chart of ability penalties that accrue as characters age. I'm pondering a system to check randomly for loss of points at certain intervals. I'm thinking about a roll of 3d20 for each physical ability score, with a total lower than or equal to that score resulting in a loss of one point from that ability. Thus, characters with very high scores are more likely to see their performance slip. The check would be made every five years between ages 30-50, every two years from 50-70, and every year thereafter. You're just not going to see many people past the age of 50 with an 18
Strength, even if they were that powerful in their youth. A character might actually stand to gain Wisdom with age, though, with a check on 3d6 against the character's current Wisdom every decade after 30, a result higher than the current score meaning a point gained.
You might also decide that it's harder for an old dog to learn new tricks, and impose a 5 or 10% penalty to earned XP to simulate this. If the party is of mixed ages, with older characters adventuring alongside young ones, this can help to offset the advantages of trade skills and extra starting resources, if you allow them.